1. Technical Field of the Invention
The present invention relates generally to an engine control system which may be employed in automotive vehicles and is designed to manage the schedule of execution of a sequence of engine control tasks.
2. Background Art
There are known schedule management systems which work to manage the schedule of a sequence of engine control tasks to control an operating condition of an automotive internal combustion engine. When receiving a request to execute a second one of the engine control tasks during execution of a first one of the engine control tasks, the system defers the execution of the second engine control task so as not to interfere with that of the first engine control task.
For instance, when a small quantity fuel injection learning task, as taught in Japanese Patent First Publication No. 2005-155360, is being executed as one of the engine control tasks when an internal combustion engine is decelerating, and no fuel is being injected into the engine, the system needs to defer the execution of the other engine control tasks until completion of the small quantity fuel injection learning task. The small quantity fuel injection learning task is to instruct a fuel injectors to spray a small quantity of fuel into the engine and calculate an actually sprayed quantity of the fuel to learn an injection characteristic of the fuel injector.
The execution of one of the engine control tasks to which an execution condition provides a higher priority to initiate or which is greater in required control execution time ratio, as will be described later in detail, prior to the other engine control tasks will, however, result in decreased chances to process the other engine control tasks.
Particularly, when the engine is decelerating, and no fuel is being sprayed into the engine, disturbances are usually small, so that lots of requests are made to commence the small quantity fuel injection learning task or the other engine control tasks, the system needs to defer the execution of the second or following engine control tasks until completion of the first one, thus limiting the chances of processing them.
When the schedule of execution of the engine control tasks which are requested to start is fixed, it may result in a difficulty in rescheduling the engine control tasks in view of the status of execution thereof for a subsequent execution cycle.